I am trying to connect to a MS SQL 2005 Database SQL server that is on a VM from my local MS SQL 2008 SSMS. i connect using object explorer > Database engine and give the sql server authentication > login > sa and PWD but it throws me an error

"cannot connect to server

additional information is required

a network related or instance-specific error...."

But i am able to RDP into that machine and login with the same sa and pwd and it connects....